NEW HAVEN — A grim new genre is taking shape as theater artists confront the plague of our age: episodes of mass murder by unhinged loners with a grievance and a gun.

Last fall, Boston’s ArtsEmerson presented a newly expanded version of “columbinus,’’ a 2005 play by Stephen Karam and PJ Paparelli that re-created the atmosphere of terror surrounding the 1999 slaughter of a dozen students and a teacher at Columbine High School by two armed youths, who then killed themselves.

Now comes David Greig’s “The Events,’’ which is jolting in a very different way. A quietly moving drama that is devoid of shock effects but loaded with heartache, “The Events’’ explores the tortured aftermath of a killing spree by a young man who entered a rehearsal of an ethnically diverse choir and began firing away. Though fictional, Greig’s play taps into the widespread feelings of sadness, anger, helplessness, and sheer bewilderment so many feel in the face of unceasing gun violence. But the playwright also suggests there are strengths we can draw upon from the bonds of community.

“The Events’’ carries echoes of a nightmarish instance of real-life violence: the massacre in Norway three years ago of 77 people, most of them teenagers, by an extremist who espoused hatred of Muslims and multiculturalism. Directed with keen attention to nuance by Ramin Gray, the US premiere of “The Events’’ is being presented through Saturday at Yale Repertory Theatre as part of the International Festival of Arts & Ideas.

For all of the emotions it brings to the surface over the course of its 80 minutes, “The Events’’ is a relatively muted, almost prayerful work. It focuses primarily on two characters: Claire, a gay minister and choir leader who survived the shooting and is portrayed by Derbhle Crotty, and a figure called only The Boy, played by Clifford Samuel, who also shoulders several other roles, including Claire’s girlfriend, a psychologist, an author, and a far-right politician.

In a very effective touch, a different local chorus is featured onstage in each performance (on opening night it was the New Haven Chorale), singing alternately subdued and soaring songs composed by John Browne. When Claire describes how she felt when the gunman burst into the choir rehearsal room, the chorus sings quietly beneath her words.

As she tries to return to everyday life and some semblance of normality, Claire keeps struggling to come to grips with the killer’s mind and motive. She is especially haunted by something he said near the end of the massacre, as he stood pointing a gun at her and another woman. “Is he mad, or is he evil?’’ she asks, adding: “I don’t want to understand what happened to me. I know what happened to me. I want to understand what happened to him.’’ The play follows Claire on that roundabout journey, including her inquiry into his background (turns out he was bullied in school), her alternate-scenario fantasy about a way she could have stopped the massacre, and, eventually, an encounter in prison with the killer.

With exquisite skill and sensitivity, Crotty conveys the jagged contours of Claire’s ravaged emotional state and her unappeasable need to get to the bottom of the event that shattered her life. Samuel is equally impressive as The Boy, alternating between antic mockery and dead-eyed indifference as he ranges across and around the stage.

As for the playwright, Greig is one versatile fellow. Two summers ago, the International Festival of Arts & Ideas presented his phantasmagorical “The Strange Undoing of Prudencia Hart’’ in a New Haven tavern. “Prudencia Hart’’ is a satirical yet eerie tale of an academic’s dalliance with the devil, written in ballad-like verse and heavily flavored with folk music. “The Events’’ is wholly dissimilar in subject, tone, and setting, but it will prove equally hard to dislodge from your memory.

Not that you should want to, because Greig poses important questions about justice, survival, retribution, forgiveness, the roots of violence, the limits of psychiatry, and the dangers of political demagoguery. He subtly asks whether we bear some collective culpability for the madness in our midst (the epigraph to his script, from Shakespeare’s “The Tempest,’’ is: “This thing of darkness I acknowledge mine’’), and whether it’s possible to find a life-affirming way forward amid the lethal insanity we have almost come to regard as routine.

Admirably, the playwright does not embrace cheap or easy answers to any of these thorny questions. Near the end of “The Events,’’ Claire gets to pose some insistent queries of her own to The Boy, all of which boil down to one word: “Why?’’ It’s a question that reverberates well beyond the Yale Rep.